nimforum mirror - How do you write a typed macro?

jxy (orginal) [2016-08-02T06:01:56+02:00] view original

Trying macro with a typed argument:

import macros
macro m(n:typed):stmt =
  echo n.treerepr
  proc p(n:NimNode) =
    for i in 0..<n.len: n[i].p
    if n.kind in CallNodes:
      for i in 1..<n.len:
        if n[i].kind in AtomicNodes:
          n[i] = newCall(bindsym"float",n[i])
  n.p
  result = n
  echo result.treerepr
var a = 1
proc f(x:int) = echo "f_int ",x
proc f(x:float) = echo "f_float ",x
m f a

The compiler errors:


t_typedmacro.nim(16, 5) Error: internal error: genMagicExpr: mFloat
No stack traceback available
To create a stacktrace, rerun compilation with ./koch temp c <file>

I guess f is still the wrong symbol, so I tried the following,

import macros
macro m(n:typed):stmt =
  echo n.treerepr
  proc p(n:NimNode) =
    for i in 0..<n.len: n[i].p
    if n.kind in CallNodes:
      n[0] = ident($n[0])
      for i in 1..<n.len:
        if n[i].kind in AtomicNodes:
          n[i] = newCall(bindsym"float",n[i])
  n.p
  result = n
  echo result.treerepr
var a = 1
proc f(x:int) = echo "f_int ",x
proc f(x:float) = echo "f_float ",x
m f a

Now the compiler segfaults:


SIGSEGV: Illegal storage access. (Attempt to read from nil?)

I guess the type is not rechecked? It works if I rebuild the call:

import macros
proc c(x:int):float = float(x)
macro m(n:typed):stmt =
  echo n.treerepr
  proc p(n:NimNode) =
    for i in 0..<n.len:
      n[i].p
    if n.kind in CallNodes:
      n[0] = ident($n[0])
      for i in 1..<n.len:
        if n[i].kind in AtomicNodes:
          n[i] = newCall(bindsym"c",n[i])
  n.p
  result = newCall("f")
  for i in 1..<n.len:
    result.add n[i]
  echo result.treerepr
var a = 1
proc f(x:int) = echo "f_int ",x
proc f(x:float) = echo "f_float ",x
m:
  # Try to change it into f(g(a))
  # Need the type of a to choose the correct g
  f a

With a statementlist

import macros
proc c(x:int):float = float(x)
macro m(n:typed):stmt =
  echo n.treerepr
  proc p(n:NimNode) =
    for i in 0..<n.len:
      n[i].p
    if n.kind in CallNodes:
      n[0] = ident($n[0])
      for i in 1..<n.len:
        if n[i].kind in AtomicNodes:
          n[i] = newCall(bindsym"c",n[i])
  proc recall(n:NimNode) =
    for i in 0..<n.len:
      n[i].recall
      if n[i].kind in CallNodes:
        var nn = newCall n[i][0]
        for j in 1..<n[i].len:
          nn.add n[i][j]
        n[i] = nn
  n.p
  n.recall
  result = n
  echo result.treerepr
var a = 1
proc f(x:int) = echo "f_int ",x
proc f(x:float) = echo "f_float ",x
m:
  # Try to change it into f(g(a))
  # Need the type of a to choose the correct g
  f a
  f a

it breaks again:


SIGSEGV: Illegal storage access. (Attempt to read from nil?)

I actually have to rebuild the statementlist for it to work:

import macros
proc c(x:int):float = float(x)
macro m(n:typed):stmt =
  echo n.treerepr
  proc p(n:NimNode) =
    for i in 0..<n.len:
      n[i].p
    if n.kind in CallNodes:
      n[0] = ident($n[0])
      for i in 1..<n.len:
        if n[i].kind in AtomicNodes:
          n[i] = newCall(bindsym"c",n[i])
  proc recall(n:NimNode) =
    for i in 0..<n.len:
      n[i].recall
      if n[i].kind in CallNodes:
        var nn = newCall n[i][0]
        for j in 1..<n[i].len:
          nn.add n[i][j]
        n[i] = nn
  n.p
  n.recall
  result = newstmtlist()
  for i in 0..<n.len: result.add n[i]
  echo result.treerepr
var a = 1
proc f(x:int) = echo "f_int ",x
proc f(x:float) = echo "f_float ",x
m:
  # Try to change it into f(g(a))
  # Need the type of a to choose the correct g
  f a
  f a

This seems to be a very contrived way of doing it. What is the standard practice of dealing with macros of typed arguments?

One more question: what does the return type of a macro mean? It doesn't seem to change anything, if I change it to typed or untyped.

Mirror of forum.nim-lang.org

2431 :: How do you write a typed macro?